This research project will develop a novel approach to targeting transgene activity to tumors using adenoviral gene transfer. Specifically, we will synthesize, evaluate, optimize, and apply novel targeting agents that are capable of high level signal amplification of imaging reporters from the viral vector. This research draws on foundations in peptide and antibody targeting of tumors, as well as advances in de-targeting of adenoviral vectors to the normal CAR and heparan sulfate glycosaminoglycan receptors by fiber mutations. Recombinant protein and adenoviral vector technology will be used to modify those interactions and enable us to develop specific proteins and adenoviral vectors capable of serving as molecular imaging reagents that will target the binding of virus to receptors specifically found on tumor endothelium. We believe that this novel technology can both generate new classes of highly specific tumor imaging reagents for diagnosis and detection, but also prove useful in determining the efficacy of gene therapy or other treatment regimens. Gene therapy holds great promise for treatment of cancer, and the imaging and therapy of tumors is an essential component of that strategy. However, major problems involve the selective delivery to target tissues and the biodistribution and levels of gene expression. We propose to use the novel imaging methods developed here at UT Southwestern in the Radiology Department and available through the Small Animal Imaging Resource to non-invasively assess gene transfer and tumor targeting. This research project will interact closely with the collaborating investigators to develop novel imaging agents and techniques, which will ultimately facilitate the detection of retargeted viral gene expression in tumors by bioluminescent imaging. Successful completion of these specific aims will demonstrate diverse applications for this novel platform and facilitate widespread implementation by investigators in the gene therapy and cancer imaging communities.